Studies for uses of inkjet printers wherein a liquid droplet is emitted from a nozzle of a head to land the droplet on a recording material, in various fields of production technologies, for instance, production of a color filter such as a liquid crystal display unit and a plasma display unit besides an image recording use such as character, drawing patter and photograph have begun in recent yeas.
Accordingly, demands for the performance of the inkjet printer have been increasing more and more and a demand for fine control of an emission timing independently for each head or for each nozzle in less than an unit of one pixel is also increasing. For example, in production of the color filter, each ink droplet of RGB color is needed to be landed at a predetermined position in a matrix from the nozzle of the inkjet head with an accuracy of μ order which is less than the unit of one pixel. For this reason, it is required that landing is to be controlled highly accurately by fine adjustment less than the unit of one pixel for each head or for each nozzle.    Patent document: Tokkaihei 10-147010
In order to the control emission timing independently head by head or nozzle by nozzle, it is considered that data transmission systems have to be configured independently for each head or for each nozzle.
However, in case data transmission system is configured for each head, usually, it is necessary to output a serial clock, serial data, a latch for data transmission and an emission start signal for forming a drive wave respectively from the control circuit board, and the control circuit board and the head have to be connected by a plurality of signal cables. Therefore, the plurality of signal cables have to be connected for a plurality head respectively. Consequently, there was a problem that number of signal cables becomes enormous.
Also, in case the data transmission system is configured for each nozzle, the emission start signal has to be provided for each nozzle respectively, there is also a problem that the number of the signal cable also becomes enormous.
As above, to provide the signal cable for each head or each nozzle causes bulky large head, complication of wiring design and cost increase. It is a serious issue to reduce the number of the signal cables between the control circuit board and the head while the numbers of the heads and nozzles are increasing.
There is considered a configuration that serial clock, latch and emission start signal are transferred from the control circuit board to every head in common, and only serial data is transferred for each head so as to reduce the number of signal cables.
However, in this embodiment, emission of each head can be performed only at the same timing and positioning adjustment between each head can be performed only by a pixel by changing read-out from a memory where data is stored. Therefore, the demand of highly accurate landing by controlling landing by less than one pixel was not satisfied.
Further, as for changing of the emission timing for each nozzle, there is suggested that the drive wave for each nozzle is formed from the same emission signal after elapsing of a predetermined delay time for each nozzle. However, in this case, due to a fluctuation of a speed of a relative movement between the head and the recording material, a landing position changes, thus there was a problem that the accurate landing cannot be realized.